Robot device controller for controlling position of robot

1. A controller for a robot device in which a robot moves a second member so as to adjust a relative position of the second member with respect to a first member, comprising: a visual sensor mounted on the robot; and a processor configured to: in a first control, obtain a reference image captured by the visual sensor in a state where the second member is arranged at a target position with respect to the first member, the reference image including images of a first characteristic portion of the first member and a second characteristic portion of the second member; detect a position of the first characteristic portion of the first member and a position of the second characteristic portion of the second member in the reference image; and calculate, as a first relative position amount, a difference between coordinate values of the position of the first characteristic portion and coordinate values of the position of the second characteristic portion in the reference image, the processor is further configured to: in a second control, obtain an image captured by the visual sensor in a state where the second member is arranged with respect to the first member, the image including images of the first characteristic portion of the first member and the second characteristic portion of the second member; detect a position of the first characteristic portion of the first member and a position of the second characteristic portion of the second member in the image; calculate, as a second relative position amount, a difference between coordinate values of the first characteristic portion and coordinate values of the second characteristic portion in the image; generate a movement command for operating the robot to move the second member to the target position with respect to the first member based on the first relative position amount and the second relative position amount; and operate the robot so that a position of the second member is adjusted to the target position with respect to the first member based on the movement command, wherein in the image captured by the visual sensor mounted on the robot, the coordinate values of the position of the second characteristic portion are constant, the processor is further configured to: repeat the second control so that the position of the second member approaches the target position with respect to the first member; store the coordinate values of the position of the second characteristic portion in a storage device when the position of the second characteristic portion is detected in the image captured by the visual sensor for a first time in repetition of the second control; and use the coordinate values of the position of the second characteristic portion stored in the storage device to calculate the second relative position amount for images captured by the visual sensor for second and subsequent times in the repetition of the second control.

2. The controller according to claim 1, wherein the processor calculates, in the second control, a difference between the first relative position amount of the reference image and the second relative position amount in the image, a movement direction of the position of the robot with respect to the difference between the first relative position amount and the second relative position amount is previously determined, a method for calculating a movement amount of the position of the robot with respect to the difference between the first relative position amount and the second relative position amount is previously determined, and the processor sets the movement direction and a movement amount of the position of the robot based on the difference between the first relative position amount and the second relative position amount, and generates the movement command based on the movement direction and the movement amount of the position of the robot.

3. The controller according to claim 1, wherein the robot device includes a carrier for conveying the first member, and the processor repeats the second control while the carrier conveys the first member.

4. The controller according to claim 3, wherein a movement direction and movement speed of the first member conveyed by the carrier are previously determined, and the processor generates the movement command based on the movement direction and a predefined movement amount of the position of the robot, in which the position of the robot follows the position of the first member conveyed by the carrier.

5. The controller according to claim 1, wherein the visual sensor constitutes a first visual sensor, the controller further comprises a second visual sensor mounted on the robot, wherein the processor is further configured to: in a third control, obtain a second reference image captured by the second visual sensor in a state where the second member is arranged at the target position with respect to the first member, the second reference image including images of a third characteristic portion of the first member and a fourth characteristic portion of the second member; detect a position of the third characteristic portion of the first member and a position of the fourth characteristic portion of the second member in the second reference image; and calculate, as a third relative position amount, a difference between coordinate values of the position of the third characteristic portion and coordinate values of the position of the fourth characteristic portion in the second reference image, the processor is further configured to: in a fourth control, obtain an image captured by the second visual sensor in a state where the second member is arranged with respect to the first member, the image including images of the third characteristic portion of the first member and the fourth characteristic portion of the second member; detect a position of the third characteristic portion of the first member and a position of the fourth characteristic portion of the second member in the image captured by the second visual sensor; calculate, as a fourth relative position amount, a difference between coordinate values of the third characteristic portion and coordinate values of the fourth characteristic portion in the image captured by the second visual sensor; generate a movement command for operating the robot to move the second member to the target position with respect to the first member based on the first relative position amount, the second relative position amount, the third relative position amount and the fourth relative position amount; and operate the robot so that a position of the second member is adjusted to the target position with respect to the first member based on the movement command, wherein in the image captured by the second visual sensor mounted on the robot, the coordinate values of the position of the fourth characteristic portion are constant, the processor is further configured to: repeat the fourth control so that the position of the second member approaches the target position with respect to the first member, store the coordinate values of the position of the fourth characteristic portion in the storage device when the position of the fourth characteristic portion is detected in the image captured by the second visual sensor for a first time in repetition of the fourth control, use the coordinate values of the position of the fourth characteristic portion stored in the storage device to calculate the fourth relative position amount for images captured by the second visual sensor for second and subsequent times in the repetition of the fourth control.

6. The controller according to claim 5, wherein the first visual sensor is arranged so as to capture an image of a portion arranged on one side of the second member in a predetermined direction, the second visual sensor is arranged so as to capture an image of a portion arranged on another side of the second member in the predetermined direction, wherein the predetermined direction corresponds to a direction in which the portions of the second member are aligned, and the processor determines whether an orientation of the second member with respect to the first member remains within a predetermined determination range based on the movement command generated from images captured by the first visual sensor and the movement command generated from images captured by the second visual sensor.